Plant material is commonly preserved by drying. Plant material can be dried for decorative and craft uses in the flat, between surfaces holding or pressing the material therebetween. Flowers, petals, leaves and other plant parts are typically pressed between absorbent layers of material by means of specially devised presses or simply under a convenient weight. Drying of this kind has been effected between the pages of books with others on top to effect pressing. The plant parts undergo a drying process over a period of time which can extend from days to weeks and even months depending on the nature of the material being dried and the characteristics of the absorbent layers being used.
The prior art includes apparatus that utilises microwave energy in a continuous press to effect curing of curable assemblies, for example, EP 0103396.
The prior art includes many techniques by which a wide variety of materials can be dried. Patent specification GB 2222095 (Pierson) sets out a drying technique utilising microwaves to effect heating of filter cake with a vacuum utilised to extract evaporated liquid.
The foregoing are not applicable to delicate materials such as flowers and other parts of plants.
Microwave energy has been proposed as a means of effecting drying of plant material in FR 2553873. In this process the plant material is placed between two pieces of corrugated cardboard, compressed and then placed in a microwave oven. Heating is for one to two minutes at a time, with rest periods between to enable cooling if the one to two minute heating period is insufficient. The need to cool between periods of heating slows the process down.